Uterine Drugs

Question 1

What is cervical ripening and why is it important for labor?

Answer 1

It is the softening of the cervix which is necessary for cervical dilation

Question 2

Describe the mechanism of action for oxytocin.

Answer 2

It is a nonpeptide hormone that is released during labor that binds to receptors altering transmembrane ion currents in the myometrium to cause uterine contraction.

Question 3

What adverse effects are associated with oxytocin?

Answer 3

Uterine tachysystole (excessively frequent contractions- 6+ in 10 minutes)

Question 4

Describe the mechanism of action of prostaglandins (misoprostol).

Answer 4

It is a PGE1 that causes uterine stimulation throughout all of gestation and ripens the cervix

Question 5

What is the clinical indication for misoprostol?

Answer 5

Labor induction and postpartum hemorrhage prevention. Used to induce contractions after a missed/incomplete miscarriage in early pregnancy.

Question 6

When is misoprostol contraindicated?

Answer 6

In women with previous c-sections

Question 7

What are common side effects associated with misoprostol?

Answer 7

GI smooth muscle contraction (n/v/d) is common. Bleeding is also possible.

Question 8

Describe the mechanism of action of ergot alkaloids (methylergometrine).

Answer 8

It is a partial agonist/antagonist at alpha-adrenergic, DA, and 5-HT receptors resulting in vasoconstriction, increased uterine motor activity (force and frequency), and high doses lead to sustained contraction

Question 9

What adverse effects are associated w/ methylergometrine (ergot alkaloids)?

Answer 9

Elevated BP, n/v are common

Question 10

With what other medication can you use methylergometrine (ergot alkaloids)?

Answer 10

Oxytocin

Question 11

What are the clinical indications for ergot alkaloids (methylergometrine)?

Answer 11

It is used to prevent postpartum hemorrhage and prolongs uterine contractions.

Question 12

When is methylergometrine (ergot alkaloids) contraindicated?

Answer 12

Hypertension (b/c this drug causes vasoconstriction)

Question 13

Name the tocolytics and the clinical indication for their use.

Answer 13

Magnesium sulfate, terbutaline, nifedipine, atosiban, and indomethicin. They are used to delay preterm delivery to allow time for corticosteroid administration for fetal lung development

Question 14

What is the general mechanism of action for tocolytics?

Answer 14

They decrease smooth muscle contractions.

Question 15

What is the mechanism of action of magnesium sulfate?

Answer 15

It is a Ca++ channel blocker that subsequently decreases strength and frequency of uterine contractions

Question 16

What is the mechanism of action of terbutaline?

Answer 16

It is a beta-2 agonist that inactivates myosin light-chain kinase resulting in relaxation of uterine muscle

Question 17

Discuss the clinical indications for magnesium sulfate.

Answer 17

It is a tocolytic used for preterm labor before 32 weeks, however it is more commonly used to prevent seizures in preeclampsia and is neuroprotective for the premature fetus.

Question 18

What adverse effects are associated with magnesium sulfate?

Answer 18

It has a narrow therapeutic index and must monitor blood plasma levels closely for hypermagnesemia, particularly in renal patients. It can also cause pulmonary edema.

Question 19

What adverse effects are associated with terbutaline?

Answer 19

It can cause reflex tachycardia and in high doses, B1 effects and hypotension. It’s adverse effects to mom and baby limit use.

Question 20

Name the antenatal corticosteroids and their clinical use.

Answer 20

Dexamethasone and betamethasone. They are used to enhance fetal lung development in preterm labor. Tocolytics are given to allow time for these medications to be administered

Question 21

Name the uterotonics and the major clinical indication for this class of drugs.

Answer 21

Oxytocin, Prostaglandins (Misoprostol), and Ergot Alkaloids (Methylergometrine). They are used to induce labor once cervical ripening is complete, and also help treat/prevent postpartum hemorrhage.

Question 22

What is the mechanism of action of Nifedipine?

Answer 22

It is a Ca++ channel blocker.

Question 23

What is the mechanism of action of indomethicin?

Answer 23

It is an NSAID aka it inhibits prostaglandins

Question 24

What is the mechanism of action of atosiban?

Answer 24

It is an oxytocin inhibitor